Here we were able to
Here, we were able to show for the first time that stimulation of VSMCs with two different growth factors resulted in a dramatic decrease in gp130mRNA expression occurring four to six hours after stimulation with Ang II and PDGF-BB. The mRNA level remained extremely low within 12 hours after stimulation. However, the question remains to be elucidated whether the growth factor-induced decrease in the gp130-related mRNA occurred due to an effect of growth factors on either transcription rate or/and on mRNA stability. Furthermore, it should be clarified by Western analysis using gp130antibodies whether an attenuation of the mRNA is also associated with a decreased level of the gp130protein.
Recently, it has been reported that monoclonal antibodies, denoted as RB13-6, recognize a subset of rat glial precursor cells that are highly susceptible to malignant conversion by the carcinogen -ethyl--nitrosourea . The corresponding cell surface rat neural differentiation and tumor cell surface antigen was purified from neuroectodermal rat cell line BT4Ca and identified as a membrane glycoprotein (gp130; ). Amino Fumagillin sequence derived from cDNA showed that gp130 is related to the human and murine plasma-cell differentiation antigen-1 (PC-1), which has been shown to possess nucleotide pyrophosphatase/alkaline phosphodiesterase and ectoprotein kinase activity , . Like PC-1, gp130possesses nucleotide pyrophosphatase activity . Although the physiological function of gp130protein is unclear, there is evidence that gp130may be involved in cell adhesion, cell motility and subversion of cells in malignant phenotypes , , , . Recently, the alkaline phosphodiesterase I (APDE) expressed in plasma membrane of rat hepatocytes and enterocytes has been identified. The APDE mRNA sequence is identical with the sequence of gp130, with the exception of a single base . Now, it has been establishhed that the alkaline phosphodiesterase/nucleotide pyrophosphatase gp130is a member of a new protein family including the plasma cell membrane glycoprotein, PC-1 , and the tumor cell motility factor, autotaxin . The gene was found in chromosome 1 and given the symbol for phosphodiesterase/nucleotide pyrophosphatase associated with neuro-oncogenesis . It is well established that PDGF-BB and Ang II are potent growth factors , , , and promote migration of VSMCs , . Using the DD method we identified a gp130-related mRNA in rat VSMCs and its expression is drastically regulated by both growth factors. Like gp130, the sequence of the cDNA fragment further shows a 58% identity with the mouse plasma cell Pc-1 cDNA and a 66% identity with human PC-1. Therefore, we suggest that the gp130-related protein in VSMCs probably possesses a phosphodiesterase/nucleotide pyrophosphatase activity and its expression is strongly regulated by PDGF-BB o Ang II. Furthermore, expression of gp130-related protein may be involved in the regulation of VSMC proliferation and migration processes induced by PDGF-BB or Ang II . However, further experiments including biochemical characterization of the protein are required to elucidate the main role of the gp130-related gene in VSMCs.
Concluding from the above, the DD method offers a powerful technique for searching for differentially expressed mRNAs that are involved in the regulation of cell growth. Applying this technique we identified a gp130-related gene the expression of which is markedly regulated by two growth factors acting distinct signaling transduction pathways.
Introduction There are two major classes of inorganic pyrophosphatases (PPases, EC 3.6.l.1), soluble PPases and membrane-associated H+-translocating PPases (H+-PPases). H+-PPases occur widely in various organisms and have a vital role in energy metabolism through hydrolysis of the inorganic pyrophosphate (PPi) released from the metabolic pathways of glucose, nucleic acids and proteins etc. H+-PPase is located on the membranes of plant vacuoles and is known as vacuolar-type inorganic pyrophosphatase (V-PPase), and acts as a H+-pump . V-PPase and vacuolar H+-ATPase (EC 3.6.l.3) are the most abundant proteins on the vacuolar membranes of plant cells, and function as parallel H+-pumps that transport H+ into the lumen of the vacuole from the cytosol and generate vacuolar acidification, leading to the electrochemical potential across the vacuolar membrane that allows the transport of many metabolites via secondary symport and antiport transporters and channels , , , .